Amongst common athletic injuries, those to the ankle have largely been overlooked in sports safety research. This is presumably because 85% of ankle injuries are sprains that are considered to be relatively minor type of injury. A further contributing factor to this lack of interest is the fact that ankle taping has proven effective in inhibiting injuries to the ankle.
While the use of tape is effective in inhibiting ankle injuries, the tape itself is expensive and its proper application requires a knowledgeable and skilled individual. The consequence of this is that recreational athletes and most of those participating in sports below the intercollegiate and national levels rarely have any significant precautions taken to protect their ankles.
The present invention aims at the provision of an athletic shoe that incorporates means for inhibiting ankle injuries. Other proposals for this type of shoe have been made. These include the proposal of U.S. Pat. No. 3,327,410 issued June 27, 1967 to H. W. Park Sr. et al. The patent discloses an integrated ankle brace and shoe. The shoe has a stiff sole and the brace is a wide strap that is fixed to the sole beneath the arch of the foot and wraps around the foot and ankle in a figure eight configuration inside the boot. This arrangement is cumbersome and will restrict the normal biomechanical movement of the foot, such as pronation and supination of the forefoot and plantarflexion and dorsiflexion of the foot.
Another proposal is disclosed in U.S. Pat. No. 3,613,273 issued Oct. 19, 1971 to R. T. Marquis. The athletic boot disclosed in that patent has combined elastic and inelastic straps extending from the sole of the boot, up the outside of the ankle to the leg above the ankle. The strap may be located either inside or outside of the boot. The major disadvantage of this reinforcement is that it does not inhibit undue strain on the anterior talofibular ligament which is the most likely to sprain in an athletic injury. The strap reinforces the calcaneo fibular ligament that is normally subject to secondary sprain after the anterior talofibular ligament, upon further inversion of the foot.
The typical ankle injury mechanism in sports is one of plantarflexion and inversion of the foot. In the plantarflexed foot, the anterior talofibular ligament, being parallel to the long axis of the talus, is placed under tension directly proportional to the degree of plantarflexion. The calcaneofibular ligament, being almost perpendicular to the talus, is proportionally relaxed. In the neutral or dorsiflexed position, the anterior talofibular ligament fibres are under no abnormal tension whereas the calcaneofibular is under tension which will increase with greater inversion. Thus the forced inversion of the plantarflexed foot results in tension of both the anterior talofibular and calcaneo talofibular ligaments that will depend upon the degree of angular rotation acting on the foot. As a rule of thumb, it can be said that the anterior talofibular ligament is normally the first to be damaged by plantarflexion and forced inversion, followed by the calcaneofibular ligament. The present invention aims at the provision of an athletic shoe that takes this injury mechanism into consideration and provides appropriate reinforcement to inhibit injuries to the ligaments in question, without excessively restricting the normal mobility of the forefoot.